The purpose of this project is to learn more about the role of membrane structure and metabolism in affecting membrane function. Using as a model system the ciliate Tetrahymena pyriformis, we plan to continue studying the regulation of membrane lipid and protein composition. A continuation of our previous experimentation on the effects of environmental factors, such as temperature, salinity, and drugs, upon membrane physical properties and lipid composition is expected to provide further insight into the molecular mechanisms whereby typical membrane helps to control cellular processes. Specific projects for the coming year incluue a) a quantitative study of the fluidity of several membranes thrugh the use of fluorescence polarization measurements, b) a study of how the changing activity of the fatty acid desaturase enzymes modifies membrane fluidity, c) the response of cellular membranes to fluidity alteration by the inhalation anesthetic methoxyflurane and other compounds, and d) regulation of the rate of vacuolar membrane formation. BIBLIOGRAPHIC REFERENCES: Thompson, G.A., Jr., C.E. Martin, R. Kasai, Y. Kitajima, K. Hiramitsu, L. Skriver, and Y. Nozawa, Proceedings, Japanese Conference for the Biochemistry of Lipids 18:167-169 (1976). The Molecular Control of Membrane Fluidity During Temperature Acclimation in Tetrahymena (abstract). Kitajima, Y. and G.A. Thompson, Jr., Journal of Cell Biology (1977) in press. Electron Microscopic Evidence that Tetrahymena Strives to Maintain the Fluidity Interrelationships of All Its Membranes Constant in a Changing Environment.